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Microbiology > M8- Oral streptococci > Flashcards

M8- Oral streptococci Flashcards

1
Q

what flora does the mouth have?

A

complex microbial flora

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2
Q

how does oral flora vary?

A

vary from site to site and in disease

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3
Q

Give some examples of gram +ve cocci.

A 
• Aerobic - Micrococcus 
• Anaerobic - Peptococcus
- Peptostreptococcus
•  Facultative
Catalase +ve Staphylococcus
Catalase –ve Streptococcus
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4
Q

what bacteria is found most in the mouth and can be cultivated from all oral sites?

A

oral streptococci

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5
Q

how does streptococci comprise?

A
  • 23% bacteria of approximal dental plaque
  • 30% bacteria of gingival crevice
  • 50% bacteria of the tongue
  • 50% bacteria of saliva
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6
Q

how does strep as facultative anaerobe effectively damage the tooth?

A

by product is lactic acid which causes damage to tooth surface

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7
Q

what type of anaerobes can strep species be?

A

Facultative & Obligate anaerobes

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8
Q

what are the 4 main groups of strep species?

A
  • mutans
  • salivarius
  • anginosus
  • oralis
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9
Q

which 3 groups are alpha haemolytic?

A
  • mutans
  • salivarius
  • oralis (Mitis)
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10
Q

what group is beta haemolytic?

A

anginosus

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11
Q

where is S. mutans found?

A

tooth surface (fissures)

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12
Q

where is S. salivarius found?

A

tongue

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13
Q

where is S. anginosus found?

A

dental plaque and abscesses

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14
Q

where is S. oxalis found?

A

tooth (biofilm/plaque)

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15
Q

what percentage of each strep species makes up 23% of bacteria of approximate dental plaque?

A

– mutans streptococci -2%
– S. sanguinis -6%
– S. salivarius- 1%
– S. anginosus gp. -0.5%

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16
Q

what haemolysis is oral or viridian’s streptococci ?

A

alpha

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17
Q

what haemolysis is pathogenic streptococci ?

A

beta

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18
Q

how does alpha look on a blood agar plate?

A
  • Partial haemolysis - green

- most oral strep

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19
Q

how does beta look on a blood agar plate?

A
  • complete hemolysis - clear haemolysis

- S pyrogens

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20
Q

how does gamma look on a blood agar plate?

A
  • No hemolysis

- eneterococcus faecalis

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21
Q

what is dental caries?

A

Localised dissolution of the enamel

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22
Q

where can caries advance to?

A

dentine and pulp

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23
Q

where is dental caries common?

A

pits and fissures (stagnation sites)

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24
Q

What causes demineralisation of enamel?

A

Bacteria under anaerobic conditions are using carbohydrate and producing lactic acid which dissolves enamel

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25
Q

what Step group is the leading cause of tooth decay?

A

mutans group

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26
Q

what species are in the mutans group?

A
  • streptococcus mutans

- S. sobrinus

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27
Q

what does mutans bind to?

A

bind to and colonise the tooth surface - produce extracellular polysaccharides (sucrose)

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28
Q

what is acidogenic?

A

produces acid at a high rate from sugar

29
Q

what is aciduric?

A

tolerate high concentrations of acid

30
Q

Name some carbohydrates.

A
  • Glucose
  • Fructose
  • Sucrose
  • Lactose
  • Galactose
  • Mannose
  • Celliobiose
31
Q

Explain Koch’s postulates.

A
  • The microorganism is present in every case of the disease but absent from healthy organisms
  • The suspected organism must be isolated and grown in a pure culture
  • The same disease must result when the isolated microorganism is inoculated into a healthy host
  • The same microorganism must be isolated again from the diseased host.
  • The Ab to the organism should be detected in the patient’s serum
32
Q

what can be used to identify patients susceptible to dental caries?

A

mutans streptococci count kits

33
Q

what is the heterogeneous group of related strep?

A

Oralis (or Mitis group)

34
Q

Name 3 species in the oralis group.

A
  • S. oralis
  • S. sanguines
  • S. gordonii
35
Q

what do most of the oxalis group produce?

A

IgA protease (important virulence factor)

36
Q

what does S. sanguinis and S. gordonii produce?

A

produce extra-cellular soluble & insoluble glucans

37
Q

when does the oxalis group colonise on the pellicle?

38
Q

What disease can strep. sanguinis result in?

A

bacterial endocarditis

39
Q

how does Strep sanguinis bind to the tooth surface?

A

by lectin-carbohydrate & non-lectin

40
Q

what does Strep sanguinis bind?

A

salivary amylase and IgA

41
Q

what does Strep sanguinis act as?

A

tether for other bacteria

42
Q

what can Strep sangunins interfere with?

A

may interfere with colonization by S. mutans

43
Q

How can S. sanguinis cause endocarditis?

A

• S. sanguinis enters the blood after oral trauma
– e.g. tooth extractions, subgingival scaling, toothbrushing and chewing, bacteraemia
• Bacteria settle on damaged endocardial surfaces causing a bacterial vegetation
– i.e. - infective endocarditis

44
Q

what was historically used to treat endocarditis?

A

Historically antibiotics used for at risk patients
– Prophylaxis antibiotics 1 hour before dental treatment
• No longer recommended by NICE!

45
Q

what is strep gordonii closely related to?

A

S. sanguinis

46
Q

what does strep gordonii produce?

A

alpha amylase

instead of S. sanguinis which produces IgA protease

47
Q

what does alpha amylase binding do?

A

marks bacterial surface antigens and allows the organism to evade the host defences

48
Q

what can Strep gordonii bind to on the tooth surface?

A

polysaccharides and starch already deposited on the tooth surface

49
Q

what does strep gordonii cause?

A

infective endocarditis

50
Q

what does PadA surface protein do?

A
  • adhesion

- interacts with platelets via fibrinogen receptor

51
Q

where is strep mitis found?

A

Although found in dental plaque, preference of non-keratinized surfaces in the mouth
– cheek,ventral surface of the tongue

52
Q

what can strep mitis cause?

A

bacteraemia, endocarditis and abscesses

53
Q

Describe strep crista.

A

• Similar to S. sanguinis but with tufts of fibrils on
surface
• Classically component of “corn-cobs” - bacterial complexes often seen in dental plaque

54
Q

what are the isolation frequencies of streptococci from infective endocarditis?

A 
S. sanguinis -32% 
S. oralis- 30% 
S. gordonii -13% 
Others:
- no other species exceeds 5%
55
Q

Name the dominant species in oral cavity throughout life isolation ; mouth, upper respiratory tract and GI tract.

A

S. salivarius

56
Q

what surfaces does salivarius group prefer?

A

Keratinised surfaces:
– Commonly found on dorsum of the tongue and in saliva
– One of the first bacteria to colonise in the mouth - within hours of birth

57
Q

where is S salvarius not normally found?

A

plaque
– does not stick to teeth
– Pili, fibrils, saliva binding proteins & host cell binding proteins
– produces fructose polymers (levans) and not glucans as the polysaccharide

58
Q

How can S salvarius be beneficial microbes?

A

Some strains produce Bacteriocins – Small antimicrobial peptides
– Salivaricin A & Salivaricin B

59
Q

what infections can salvarius be associated with?

A

Pharyngitis, tonsillitis, otitis media

60
Q

Describe S. vestibularis.

A

• Non-pathogenic, non-polysaccharide producing – inhabitant of the oral vestibular mucosa

61
Q

Name species in the anginosus group.

A

S. anginosus
S. constellatus
S. intermedius
(opportunistic pathogens)

62
Q

where are the anginosus group found?

A

dental plaque

63
Q

what infections are anginosus group species isolated from?

A

– oral abscesses & brain, liver
– bacteraemia and endocarditis
– appendicitis and peritontitis

64
Q

what are the different habitats of oral streptococci species?

A

S. sanguinis, S. mutans - tooth surfaces
S. salivarius - salvia and tongue
S. mitis -oral epithelia

65
Q

Describe S pneumoniae .

A

– α-haemolytic
– N.B. sensitive to optochin
– carriage as high as 70%
– spread by coughing/sneezing

66
Q

what is sensitive to bacitracin?

A

S. pyroxenes (beta)

67
Q

what is resistant to bacitracin?

A
  • S. pneumoniae (alpha)
  • Viridans (alpha)
  • E. facials (gamma)
68
Q

what is sensitive to optochin?

A

S. pneumoniae

69
Q

what is resistant to optochin?

A
  • S. pyogenes
  • Virdians
  • E. facealis

Microbiology (30 decks)

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